Electron Conducting Carbon-Based Cement

ABSTRACT

A nanoporous carbon-loaded cement composite that conducts electricity. The nanoporous carbon-loaded cement composite can be used in a variety of different fields of use, including, for example, a structural super-capacitor as an energy solution for autonomous housing and other buildings, a heated cement for pavement deicing or house basement insulation against capillary rise, a protection of concrete against freeze-thaw (FT) or alkali silica reaction (ASR) or other crystallization degradation processes, and as a conductive cable, wire or concrete trace.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.17/113,745, filed on Dec. 7, 2020, which is a divisional of U.S.application Ser. No. 16/245,752, filed on Jan. 11, 2019, now U.S. Pat.No. 10,875,809, which claims the benefit of U.S. Provisional ApplicationNo. 62/616,693, filed on Jan. 12, 2018. The entire teachings of theabove applications are incorporated herein by reference.

BACKGROUND

On the one hand, there is no other material that can replace cement inthe foreseeable future to meet our societies' needs for housing, shelterand infrastructure. Nevertheless, cement faces an uncertain future, dueto a non-negligible ecological footprint that amounts to 5-10% of theworldwide CO₂ production. On the other hand, thanks to breakthroughs inscience and engineering, cement has a novel potential to contribute to asustainable development encompassing economic growth and social progresswhile minimizing the ecological footprint.

SUMMARY

In accordance with an embodiment of the invention, there is provided ananoporous carbon-loaded cement composite that conducts electricity. Thenanoporous carbon-loaded cement composite can be used in a variety ofdifferent possible fields of use, including, for example: a structuralsuper-capacitor as an energy solution for autonomous housing and otherbuildings; a heated cement for pavement deicing or house basementinsulation against capillary rise; a protection of concrete againstfreeze-thaw (FT) or alkali silica reaction (ASR) or othercrystallization degradation processes; and as a conductive cable, wireor concrete trace.

In one embodiment according to the invention, there is provided anelectrically conductive cement composite, comprising hydraulic cement,water, a carbon nanoparticle dispersing agent, and a continuouspercolating network of nanoporous carbon nanoparticles.

In further, related embodiments, the electrically conductive cementcomposite may comprise between about 2% by weight and about 10% byweight of the nanoporous carbon nanoparticles with respect to a totalinitial mix comprising the hydraulic cement, the carbon nanoparticledispersing agent, the water and the nanoporous carbon nanoparticles, andcomprise a water to cement ratio between about 0.5 and about 0.8. Thecarbon nanoparticle dispersing agent may comprise carboxymethylcellulose. The carboxymethyl cellulose may comprise between about 0.1%by weight and about 1% by weight of a total initial mix comprising thehydraulic cement, the carbon nanoparticle dispersing agent, the waterand the nanoporous carbon nanoparticles. The nanoporous carbonnanoparticles may comprise a carbon material comprising a dominatingpopulation of carbon atoms engaged in sp²-hybridization. The nanoporouscarbon nanoparticles may comprise a pore size of less than about 1nanometer. The nanoporous carbon nanoparticles may comprise at least oneof: Vulcan carbon black, Ketjen carbon black, PBX carbon black and anactivated porous carbon. The hydraulic cement may comprise PortlandCement. The electrically conductive cement composite may comprisebetween about 50% by weight and about 70% by weight of Portland Cement,such as about 60% by weight of Portland Cement, with respect to a totalinitial mix comprising the hydraulic cement, the carbon nanoparticledispersing agent, the water and the nanoporous carbon nanoparticles. Theelectrically conductive cement composite may comprise an electricalresistivity of less than about 1000 ohm-meters, such as less than about300 ohm-meters. The continuous percolating network of nanoporous carbonnanoparticles may substantially fill a capillary pore network of theelectrically conductive cement composite, the capillary pore networkcomprising pores between about 5 nanometers and about 1 micron in size.The electrically conductive cement composite may comprise a greater than90 percent connected percolating pore network that hosts the nanoporouscarbon nanoparticles which form the continuous percolating network ofnanoporous carbon nanoparticles. The nanoporous carbon nanoparticles maycomprise a specific surface area less than about 3000 m²/g, such as lessthan about 300 m²/g. The electrically conductive cement composite maycomprise between about 0.1% by weight and about 1% by weight of thecarbon nanoparticle dispersing agent with respect to a total initial mixcomprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles.

In another embodiment according to the invention, there is provided anelectrically conductive mortar, the mortar comprising fine aggregate andany of the electrically conductive cement composites taught herein.

In another embodiment according to the invention, there is provided anelectrically conductive concrete, comprising sand, gravel aggregates,and any of the electrically conductive cement composites taught herein.

In a further embodiment according to the invention, there is provided astructural supercapacitor, comprising at least two conductors comprisingany of the electrically conductive cement composites taught herein,separated by a dielectric porous medium permeable to electrolytespecies.

In further related embodiments, the structural supercapacitor maycomprise a structural element in a building. The dielectric porousmedium may comprise a separator membrane comprising at least one ofpaper and Portland Cement. Each of the at least two conductors maycomprise a sheet comprising the electrically conductive cementcomposite, the sheet being less than about 100 cm thick, such as lessthan about 10 cm thick. The structural supercapacitor may be inelectrical connection with an energy source, such as at least one of asolar energy source, a wind power source, a biofuel energy source, abiomass energy source, a geothermal power source, a hydropower source, atidal power source and a wave power source. The structuralsupercapacitor may be in electrical connection with a battery.

In a further embodiment according to the invention, there is provided aJoule effect heated monolith structure, the structure comprising any ofthe electrically conductive cement composites taught herein and at leasttwo terminals configured to receive application of an electricalpotential difference between the at least two terminals, therebyproducing heating in the electrically conductive cement composite.

In further related embodiments, the heated monolith structure maycomprise at least a portion of at least one of a home basement wall orfloor, a pavement, a road, and an airport runway.

In another embodiment according to the invention, there is provided aconcrete resistant to crystallization induced degradations, the concretecomprising an electrically conductive concrete comprising any of theelectrically conductive cement composites taught herein and at least twoterminals configured to receive application of an electrical potentialdifference between the at least two terminals.

In a further embodiment according to the invention, there is provided aconductive cable, wire or concrete trace comprising any of theelectrically conductive cement composites taught herein.

In another embodiment according to the invention, there is provided amethod of forming an electrically conductive cement composite, themethod comprising mixing nanoporous carbon nanoparticles in an aqueoussolution of a carbon nanoparticle dispersing agent thereby creating ananoporous carbon nanoparticle suspension; and mixing a hydraulic cementpowder with the nanoporous carbon nanoparticle suspension.

In further, related embodiments, the method may further comprise castingthe electrically conductive cement composite and immersing theelectrically conductive cement composite in a solution comprising limeand water. The method may further comprise forming a compositecomprising between about 2% by weight and about 10% by weight of thenanoporous carbon nanoparticles with respect to a total initial mixcomprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles, and comprisinga water to cement ratio between about 0.5 and about 0.8. The carbonnanoparticle dispersing agent may comprise carboxymethyl cellulose. Thecarboxymethyl cellulose may comprise between about 0.1% by weight andabout 1% by weight of a total initial mix comprising the hydrauliccement, the carbon nanoparticle dispersing agent, the water and thenanoporous carbon nanoparticles. The nanoporous carbon nanoparticles maycomprise a pore size of less than about 1 nanometer. The nanoporouscarbon nanoparticles may comprise at least one of Vulcan carbon black,Ketjen carbon black, PBX carbon black and an activated porous carbon.The hydraulic cement may comprise Portland Cement. The electricallyconductive cement composite may comprise between about 50% by weight andabout 70% by weight of Portland Cement with respect to a total initialmix comprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles. The nanoporouscarbon nanoparticles may comprise a specific surface area less thanabout 3000 m²/g, such as a specific surface area less than about 300m²/g.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing will be apparent from the following more particulardescription of example embodiments, as illustrated in the accompanyingdrawings in which like reference characters refer to the same partsthroughout the different views. The drawings are not necessarily toscale, emphasis instead being placed upon illustrating embodiments.

FIG. 1 is a graph of resistivity (ρ) of various cement samples (pure,loaded with cellulose or loaded with cellulose and porous carbonnanoparticles, either Vulcan or Ketjenblack) in an experiment inaccordance with an embodiment of the invention.

FIG. 2A is a Scanning Electron Micrograph (SEM) image of a samplesurface, and FIG. 2B is a Raman map of carbon, determined in asub-region at the center of the SEM image of FIG. 2A, in an experimentto determine whether carbon nanoparticles are homogeneously distributedin the cement matrix.

FIGS. 3A and 3B are images of results from an experiment to characterizethe porosity of cement samples in accordance with an embodiment of theinvention, in which there were performed physisorption experiments ofazote at 77K, with BET surface area (FIG. 3A) and pore size distribution(FIG. 3B) being determined using the Brunauer-Emmett-Teller (BET) method(1) and the Barrett-Joyner-Halenda (BJH) method (2) on the desorptionbranch respectively.

FIGS. 4A and 4B are images of results from experiments to characterizeHardness, Indentation modulus and creep modulus of samples in accordancewith an embodiment of the invention. FIG. 4A shows Hardness (H),Indentation modulus (M) and creep modulus (C) of cement sample vs. thecontent in dimetoxycarboxy cellulose. FIG. 4(B) shows the same series ofgraphs for cement samples versus various degrees of content of Vulcannanoparticles.

FIG. 5 shows an overall procedure used in an experiment in accordancewith an embodiment of the invention, in which carboxymetylcellulosehelps to disperse large quantities of hydrophobic carbon blacknanoparticles in water.

FIG. 6 shows resistivity of hardened cement paste/nanoporous carboncomposites containing 0.6% wt. of carboxymethyl-cellulose and variousamounts of nanoporous carbon nanoparticles ranging between 0 and 8% wt,in an experiment in accordance with an embodiment of the invention.

FIG. 7 shows the resistivity of a broad collection of compositesprepared with various water to cement ratio (w/c), various amount ofcarboxymethyl-cellulose and various type and amounts of carbonnano-particles, in an experiment in accordance with an embodiment of theinvention.

FIG. 8 shows mechanical properties of hardened cement paste, i.e.distribution of Hardness H, indentation modulus M and creep modulus Cdetermined at the mesoscale (a) to (c) and at the microscale (d) to (f),in an experiment in accordance with an embodiment of the invention.

FIG. 9 shows distribution of H, M and C at the mesoscale for thereference hardened cement paste (same data as in FIG. 8 ) and for thecement paste/cellulose composite, in an experiment in accordance with anembodiment of the invention.

FIG. 10 shows distribution of H, M and C at the microscale for acement/cellulose composite (a)-(c), in an experiment in accordance withan embodiment of the invention.

FIG. 11 shows evolution at the mesoscale of the mechanical properties ofcement/carbon composites vs the amount of carbon, in an experiment inaccordance with an embodiment of the invention.

FIG. 12 shows distribution of H, M and C at the microscale for acomposite with 0.6% wt. cellulose and 5% wt carbon (a)-(c), in anexperiment in accordance with an embodiment of the invention.

FIG. 13 shows surface temperature increase of a cellulose +5% wt carbonsample under 30 V (DC), in an experiment in accordance with anembodiment of the invention.

FIG. 14 shows the capacitor effect (as obtained from cyclic voltammetryexperiment, CV) with KCl 1M as electrolyte, in an experiment inaccordance with an embodiment of the invention.

DETAILED DESCRIPTION

A description of example embodiments follows.

Embodiments of the invention are based on the discovery of a nanoporouscarbon loaded cement paste composite that conducts electricity. Thenanoporous carbon-loaded cement composite can be used in a variety ofdifferent possible fields of use, including, for example: a structuralsuper-capacitor as an energy solution for autonomous housing and otherbuildings; a heated cement for pavement deicing or house basementinsulation against capillary rise; a protection of concrete againstfreeze-thaw (FT) or alkali silica reaction (ASR) or othercrystallization degradation processes; and as a conductive cable, wireor concrete trace.

As used herein and in the accompanying claims, “hydraulic cement” is acement that sets in the presence of water and forms a water-resistantproduct. Examples include Portland cement, Portland cement blends, andcalcium sulfoaluminate cements.

As used herein and in the accompanying claims, “Portland cement” isdefined in accordance with ASTM Standard C150, the entire teachings ofwhich are hereby incorporated herein by reference. More particularly“Portland cement” as used herein and in the accompanying claims refersto hydraulic cement (cement that not only hardens by reacting with waterbut also forms a water-resistant product) produced by pulverizingclinkers which consist essentially of hydraulic calcium silicates,usually containing one or more of the forms of calcium sulphate as aninter ground addition.

As used herein and in the accompanying claims, a “carbon nanoparticledispersing agent” is an agent that disperses a carbon phase includingcarbon nanoparticles, in water. For example, carboxymethyl cellulose ora cellulose based polymer can be used.

In accordance with an embodiment of the invention, the nanoporous carbonphase can be any of the carbon material family with a dominatingpopulation of carbon atoms engaged in an sp² hybridization scheme, withexamples given below.

As used herein and in the accompanying claims, a “continuous percolatingnetwork of nanoporous carbon nanoparticles” within a cement composite isa network formed by continuous connection of carbon nanoparticles thathave percolated a capillary pore network of the cement to a sufficientdegree to make the cement composite electrically conductive. Thecontinuous percolating network of nanoporous carbon nanoparticles can,but need not, substantially or completely fill the porosity of thecapillary pore network of the cement. A capillary pore network within acement composite can, for example, include pores between about 5nanometers and about 1 micron in size.

As will be described further in connection with experiments inaccordance with an embodiment of the present invention, it has beenfound that, in order to disperse a carbon phase including carbonnanoparticles, in water, a small amount (for example, between about 0.1%by weight and about 1% in weight compared to the initial total mix) of acarbon nanoparticle dispersing agent such as Carboxy-Methyl Cellulose(CMC) can be used. This solution is then mixed with Ordinary PortlandCement (OPC) in the proportion of, for example, about 60% of OPC inweight. It will be appreciated that other proportions can be used, suchas between about 50% of OPC and about 70% of OPC by weight. The sampleis then, for example, stored during a week in a CaO solution formaturation. In experiments in accordance with an embodiment of theinvention, described in more detail below, measurements are made after asetting time of 3 weeks. In the experiments, we determine (i) theelectrical conductivity (ii) composite porosity through BETmeasurements, (iii) the mechanical properties (Hardness, Indentationmodulus and creep modulus), and (iv) electrical capacitance. Thesequantities are measured as a function of the amount of nanoporouscarbons added to the sample. We have tested various nanoporous carbons,namely Vulcan carbon black particles (specific surface area 214 m²/g,particle size 30 nm), Ketjen black particles (specific surface area 932m²/g, particle size 30 nm), multiwall carbon nanotubes (MWCN, length ofseveral microns, diameter 300 nm) and graphene flakes (size 30 nm).Other nanoporous carbon nanoparticles can be used, such as activatedporous carbons, for example AX-21, saccharose cokes and others.

As a proof of concept, it has been determined in accordance with anembodiment of the invention that the electrical resistivity of astandard cement can be decreased, for example, from 10⁷ Ωm down to 150Ωm by adding Vulcan nanoporous carbon at 2.7% in weight of the totalmix. Such effect results from a percolated network of porous carbonparticles. Indeed, low temperature Nitrogen adsorption/desorptionexperiments reveal that electron conductivity is achieved when theso-called capillary pores network of the cement paste (extending from 5nm to micron size in pore sizes) is partially filled with carbonnanoparticles. Moreover, preliminary X-ray tomography imagingexperiments (64 nm resolution) reveal that this capillary porosity incement paste constitute a greater than 90% connected percolating porenetwork.

Without wishing to be bound by theory, it is believed that having acontinuous network of nanoporous carbon particles percolating the entirecement paste is therefore a useful element to achieve an electronconductive cement paste. It is due to the fundamental de-mixing betweenorganic and setting inorganic phases formed during cement hydrationprocess.

Furthermore contrarily to iron or copper, there should be no oxidizationprocesses; therefore, the electrical conductivity should not be alteredover time.

In one embodiment according to the invention, an electrically conductivecement composite includes hydraulic cement, water, a carbon nanoparticledispersing agent, and a continuous percolating network of nanoporouscarbon nanoparticles. The electrically conductive cement composite caninclude between about 2% by weight and about 10% by weight of thenanoporous carbon nanoparticles with respect to a total initial mixcomprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles, and cancomprise a water to cement ratio between about 0.5 and about 0.8. Thecarbon nanoparticle dispersing agent can include carboxymethylcellulose, which can include between about 0.1% by weight and about 1%by weight of a total initial mix comprising the hydraulic cement, thecarbon nanoparticle dispersing agent, the water and the nanoporouscarbon nanoparticles. In another example, a cellulose based polymer canbe used as a carbon nanoparticle dispersing agent. The nanoporous carbonnanoparticles can include at least one of: Vulcan carbon black, Ketjencarbon black, PBX carbon black and an activated porous carbon, such asAX-21 or a saccharose coke; and can include a pore size of less thanabout 1 nanometer. The PBX carbon black can, for example, be PBX® 55carbon black, sold by Cabot Corporation of Boston, Mass., U.S.A. Thehydraulic cement can include Portland Cement; and the electricallyconductive cement composite can include between about 50% by weight andabout 70% by weight of Portland Cement, such as about 60% by weight ofPortland Cement, with respect to a total initial mix comprising thehydraulic cement, the carbon nanoparticle dispersing agent, the waterand the nanoporous carbon nanoparticles. The electrically conductivecement composite can include an electrical resistivity of less thanabout 1000 ohm-meters, such as less than about 300 ohm-meters. Thecontinuous percolating network of nanoporous carbon nanoparticles cansubstantially fill a capillary pore network of the electricallyconductive cement composite. The capillary pore network can includepores between about 5 nanometers and about 1 micron in size. Theelectrically conductive cement composite can comprise a greater than 90percent connected percolating pore network that hosts the nanoporouscarbon nanoparticles which form the continuous percolating network ofnanoporous carbon nanoparticles. The nanoporous carbon nanoparticles canhave a specific surface area less than about 3000 m²/g, such as lessthan about 300 m²/g. The electrically conductive cement composite caninclude between about 0.1% by weight and about 1% by weight of thecarbon nanoparticle dispersing agent with respect to a total initial mixcomprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles. Anelectrically conductive mortar can be made, that includes fine aggregateand any of the electrically conductive cement composites taught herein.An electrically conductive concrete can also be made, that includessand, gravel aggregates, and any of the electrically conductive cementcomposites taught herein.

Several fields of application of electrically conductive cementcomposites in accordance with an embodiment of the invention aredescribed below.

1. Structural Super-Capacitor as an Energy Solution for AutonomousHousing

Context: On the one hand, there is no other material that can replacecement in the foreseeable future to meet our societies' needs forhousing, shelter and infrastructure. Nevertheless, cement faces anuncertain future, due to a non-negligible ecological footprint thatamounts to 5-10% of the worldwide CO₂ production. On the other hand,thanks to breakthroughs in science and engineering, cement has a novelpotential to contribute to a sustainable development encompassingeconomic growth, social progress while minimizing on the ecologicalfootprint, if besides mechanical strength, new energy-storagefunctionalities were added to structural elements (beams, slabs) in abuilding.

Field of Application: In accordance with an embodiment of the invention,the functionality of cement paste is optimized towards electrical energystorage using our electron nanoporous/nanoparticle carbon-loadedconductive cement paste assembled in a gigantic structuralsupercapacitor.

Thus, in a further embodiment according to the invention, there isprovided a structural supercapacitor, which can be a structural elementin a building, and that includes at least two conductors comprising anyof the electrically conductive cement composites taught herein,separated by a dielectric porous medium permeable to electrolytespecies. The dielectric porous medium can include a separator membranethat includes at least one of paper and Portland Cement. Each of the atleast two conductors can include a sheet comprising the electricallyconductive cement composite, and the sheet can, for example, be lessthan about 100 cm thick, such as less than about 10 cm thick. Thestructural supercapacitor can be in electrical connection with an energysource, such as at least one of a solar energy source, a wind powersource, a biofuel energy source, a biomass energy source, a geothermalpower source, a hydropower source, a tidal power source and a wave powersource. The structural supercapacitor can be in electrical connectionwith a battery.

2. Joule Effect for Pavement Deicing/House Basement Insulation AgainstCapillary Rise

Context: It is of practical interest of addressing high conductivecement where the conductivity through a joule effect increases themonolith cement temperature due to the electronic transport. Severalapplications of first importance can be designed to eliminate wallcapillary rise of home basements and icing layers on pavement, roads orairport runways in cold temperature weather.

Field of application: Considering the cement heat capacity (1.55 kJ kg⁻¹K⁻¹), one may argue that beyond being an electronic insulator, pristinecement is also a heat insulator and it is not worth dispersing heatconductor within an insulator continuous phase, as the insulatingproperty will dominate the whole behavior, even if considering sp2 typecarbon particles bearing heat capacity around 700 J K⁻¹ kg⁻. This nolonger holds if the carbonaceous dispersion is percolated within thecement phase such as in electrically conductive cement composite design.If the carbon phase is percolated, both the electronic and heattransport will be strongly enhanced, scenario where the dispersed phasewill now completely dominate the cement/carbon composite materialsproperties. As such we may consider that the carbonaceous percolatedcontinuous phase will act as “heating highways,” due its intrinsic highheat capacity, and thus propagates the heat at ease along the wholemonolith. Furthermore, the carbon particles, contradictory to iron orcopper, should not be oxidized, thereby its intrinsic conductivityshould not be modifying neither with time, nor with the winter weatherconditions.

A preliminary experiment applying a potential difference of 30 V under0.1 A between the two sides of an electrically conductive cementcomposite cm³ electrode shows a rise in temperature of 5° C. in a fewseconds. An embodiment thereby provides the Joule effect in aCarbon-Cement-Composite.

Thus, in an embodiment according to the invention, there is provided aJoule effect heated monolith structure, which includes any of theelectrically conductive cement composites taught herein and at least twoterminals configured to receive application of an electrical potentialdifference between the at least two terminals, thereby producing heatingin the electrically conductive cement composite. The heated monolithstructure can include at least a portion of at least one of a homebasement wall or floor, a pavement, a road, and an airport runway.

3. Protection of Concrete Against Freeze-Thaw (FT)/Alkali SilicaReaction (ASR) Degradation Processes

Context for FT: Freeze-thaw damage lies in the scope of the broad fieldof Crystallization in a porous medium. More specifically, it is due todrop of temperature in winter weather conditions. It leads to concretecracking. The conditions for FT damage to occur are a water saturationof the cement pore network (at least of 80%) and the presence of ions ofthese pores (pristine ions plus deicing salts). It is known that damagesconcentrate at the joint between pavement slabs where deicing salt ionsaccumulate. The usual idea to explain FT degradation of concrete is thatit is due to ice growth inside the capillary pores at high water degreeof saturation; ice occupying a larger volume than liquid water. However,it has become clear that (i) the interface between ice and the cementpaste is an electrolytic liquid nano-layer (ii) in this nanometricliquid layer, an ionic disjoining pressure can develop between the icecore and the cement paste providing that the temperature is low enough(−8 C) for the ice to stand this pressure (otherwise it melts ice intoliquid water, the liquidus line of the water phase diagram being ofnegative slope).

Context for ASR: The mechanism by which the ASR gel is formed requires ahigh-pH solution, the presence of alkali ions, of Ca²⁺ ions and plentyof OH⁻. For a long time, it was believed that the ASR gel (i) was a veryhard material (˜0.5 stiffness of C—S—H), that can exert considerablepressure on C—S—H since it takes 10-20% more volume than the aggregategrains that it dissolves as a largely incompressible fluid that can flowin the aggregate-cement paste interfacial transition zone (ii) The gelinitially has a low-calcium content, and flows out without creatingdamage. It calcifies in the cement paste. It was suggested that thiscalcified gel layer is semi-permeable: it lets alkali ions, OH⁻ andwater flow, but does not let gel escape. The ASR reaction continues,with the additional gel produced confined by the calcified reaction rim.This leads to a buildup of expansive pressure. More recently, it wasshown by CSHub@MIT, that the gel flows into the cement paste and itexchanges ions with the nearby cement paste. Notably, the cement pastecan intake alkali ions (and loses Ca²⁺ ions), which leads to theexpansion of the cement paste nanograins themselves. However cementpaste can take a rather limited amount of alkali ions (2%), leaving thevast majority of alkali species in the capillary cement paste poressolution as the ASR gel flows from the aggregates into the cement paste.The gel surface is electrically neutral, while that of cement pastesurface is charged. The interaction of the ion-rich wetting layerin-between a charged surface and a neutral surface leads to substantialelectrostatic disjoining pressure. If the gel is not stiff enough, i.e.has a low calcium content, this pressure makes it flow into other pores.If the gel gets stiff, i.e. calcified, it can withstand this pressureand is then transmitted through the whole concrete structure. Moleculardynamics simulations carried out at the CSHub@MIT shows that thisdisjoining pressure due to alkali ions in the liquid layer between theASR gel and the cement paste can reach over 50 MPa. Portlandite, theother product of cement hydration (dissolution/precipitation reaction)is probably the main calcifying agent of the ASR gel.

Field of Application, to prevent both FT and AST or any othercrystallization induced degradations of concrete: In accordance with anembodiment of the invention, it is now understood that if one could makethe capillary pores of a cement paste hydrophobic then there will bewetting layer induced ionic disjoining pressure. The nano carbon grainsused to design the electrically conductive cement composite material inaccordance with an embodiment of the invention, are essentiallyhydrophobic hence will repel water entering the capillary pore of cementpaste. Furthermore, upon electrical polarization as for the otherembodiments described above, the electrically conductive cementcomposite material will store alkali ions. Therefore, structuralelements made the electrically conductive cement composite materialwould be not sensitive to FT and/or ASR damages any longer.

The above embodiment thereby can produce Damage-Free Concrete, or atleast a concrete resistant to crystallization induced degradations. Suchconcrete includes an electrically conductive concrete comprising any ofthe electrically conductive cement composites taught herein and at leasttwo terminals configured to receive application of an electricalpotential difference between the at least two terminals.

In another embodiment according to the invention, a conductive cable,wire or concrete trace can include any of the electrically conductivecement composites taught herein.

In another embodiment according to the invention, there is provided amethod of forming an electrically conductive cement composite. Themethod includes mixing nanoporous carbon nanoparticles in an aqueoussolution of a carbon nanoparticle dispersing agent, thereby creating ananoporous carbon nanoparticle suspension, and mixing a hydraulic cementpowder with the nanoporous carbon nanoparticle suspension. The methodcan include casting the electrically conductive cement composite andimmersing the electrically conductive cement composite in a solutioncomprising lime and water. The method can include forming a compositecomprising between about 2% by weight and about 10% by weight of thenanoporous carbon nanoparticles with respect to a total initial mixcomprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles, and comprisinga water to cement ratio between about 0.5 and about 0.8. The carbonnanoparticle dispersing agent can include carboxymethyl cellulose, whichcan be between about 0.1% by weight and about 1% by weight of a totalinitial mix comprising the hydraulic cement, the carbon nanoparticledispersing agent, the water and the nanoporous carbon nanoparticles. Thenanoporous carbon nanoparticles can have a pore size of less than about1 nanometer; and can be at least one of Vulcan carbon black, Ketjencarbon black, PBX carbon black and an activated porous carbon, such asAX-21 or a saccharose coke. The hydraulic cement can include PortlandCement. The electrically conductive cement composite can include betweenabout 50% by weight and about 70% by weight of Portland Cement, such asabout 60% by weight of Portland Cement, with respect to a total initialmix comprising the hydraulic cement, the carbon nanoparticle dispersingagent, the water and the nanoporous carbon nanoparticles. The nanoporouscarbon nanoparticles can have a specific surface area less than about3000 m²/g, such as a specific surface area less than about 300 m²/g.

Below we describe experiments conducted in accordance with an embodimentof the invention:

EXPERIMENTAL

Sample Preparation:

Cement samples loaded with carbon nanoparticles are prepared by mixingporous carbon nanoparticles (CABOT) in an aqueous solution ofdimetoxycarboxy cellulose (Sigma Aldrich), which allows for dispersingand solubilizing these hydrophobic and porous nanoparticles over atypical duration of about 24 h. Cement powder is then added to thesuspension and the sample is immediately mixed in a beaker @1200 rpm forabout 90 s. The cement paste is then cast into a polycarbonate moldsealed with parafilm at both ends before being immersed in a lime/watersolution for setting. After a week, the cement samples are solid andde-molded with a mechanic press and cut with a low-speed rotating saw inwet conditions (with the lime solution) into 6 to 7 cylinders (typicaldiameter 2r=22.5 mm, and height e=10 mm). The cylinders are stored aconstant temperature, before being used for further testing: electrical(conductivity measurements), structural (nitrogen physisorption, energydispersive X-ray spectrometry and Raman spectroscopy) and mechanical(micro-indentation). Note that reference samples made of either purecement, or cement and cellulose, are prepared following the same stepsdescribed above using respectively distilled water or aqueous solutionof dimetoxycarboxy cellulose.

Electrical Properties:

Reference samples, i.e., pure cement samples and cement samplescontaining dimetoxycarboxy cellulose both behave as electrical insulator(ρ≈10⁷ Ω. m). Same goes for cement samples containing less than 2.3% wt.of carbon nanoparticles (either Vulcan or Ketjenblack or PBX). However,cement samples containing more than about 2.3% wt. of Vulcannanoparticles show a significantly lower resistivity (ρ≈10² Ω. m), byabout 5 orders of magnitude, which proves that these carbon loadedsamples are electrically conductive. The transition between insulatorand conductor occurs in a narrow range of concentrations in carbonnanoparticles, at about 2.3% wt., which points towards the existence ofa percolation threshold. Above 2.3% wt., the Vulcan nanoparticles form apercolated network than spans over the entire cement sample. This carbonbackbone is responsible for the electrical conductive propertiesobserved macroscopically. Finally, it is worth noting that Ketjenblacknanoparticles tend to aggregate, which makes it impossible to disperseto pass the percolation threshold, even with cellulose content up to0.56% wt.

FIG. 1 —Resistivity ρ of various cement samples: pure, loaded withcellulose or loaded with cellulose and porous carbon nanoparticles:either Vulcan (VXC72R, CABOT) or Ketjenblack (CABOT) or PBX. Theelectrical resistivity ρ is measured on cement samples of cylindricalshape: typical diameter 2r=22.5 mm and thickness e=10 mm. Samples aresandwiched between two copper electrodes connected to a high precisionpotentiostat (Solartron SI1287) that allows imposing a decreasing rampof voltage from 10V to 0V, while recording the current passing throughthe sample. The voltage/current ratio is measured to be roughly constantand averaged to estimate the sample resistance R, which is thenconverted into the sample resistivity ρ using the following equation:ρ=R×πr²/e. Note that the water to cement ratio varies from 0.42 to 0.58and that the samples electrically conductive contain 0.5% wt. ofcellulose.

Distribution of Porous Carbon Particles in the Cement Matrix:

To test whether the carbon nanoparticles are homogeneously distributedin the cement matrix, we have performed Raman spectroscopy experimentsat the surface of an electrically conductive cement sample loaded with2.7% wt. of Vulcan nanoparticles and 0.5% wt. of dimetoxycarboxycellulose. The sample is polished with a sequence of SiC papers ofdecreasing abrasiveness before being fixed on a metallic stub withcyanoacrylate glue. The sample surface is imaged using a correlativeSEM/EDS Raman Microscope with a laser beam at 538 nm. A typical SEMpicture of the sample surface is reported in FIG. 2A, while a Raman mapof the carbon element, determined in a sub-region at the center of theSEM picture, is shown in FIG. 2B. The carbon nanoparticles appearhomogeneously dispersed at a scale of 10 μm, which supports the claim ofa percolated carbon network embedded into the cement matrix.

FIG. 2A: SEM image of the top surface of an electrically conductivecement sample containing 2.7% wt. of Vulcan nanoparticles and 0.5% wt.of dimetoxycarboxy cellulose. FIG. 2B: Raman map of the carbon elementin the central sub-region 200 of the SEM picture. The red regions 201correspond to the area with carbon elements. Yellow spots 202 areartefacts due to fluorescence and should be ignored.

Location of the Carbon Nanoparticles Within the Porosity of the CementMatrix:

To characterize the porosity of the cement samples, we have performedphysisorption experiments of azote at 77K. BET surface area (FIG. 3A)and pore size distribution (FIG. 3B) have been determined using theBrunauer-Emmett-Teller (BET) method (1) and the Barrett-Joyner-Halenda(BJH) method (2) on the desorption branch respectively. The specificsurface area of the cement sample increases with the content in carbonnanoparticles, since the nanoparticles are porous and show a much largersurface area (240 m².g⁻¹) than the cement matrix (35 m².g⁻¹).

FIG. 3A: BET surface area vs the content in carbon nanoparticles. Thepresence of cellulose in a cement sample increases the BET surface area.Moreover, the addition of carbon further increases the BET surface area,proportionally to the amount of Vulcan nanoparticles. Indeed, the carbonnanoparticles are porous and present a larger BET surface area (surfacearea of 240 m².g⁻¹—measured performed independently) than the cementcontaining cellulose only (surface area of 35 m².g⁻¹). FIG. 3B: Poresize distribution of a pure cement sample and of a cement sample that iselectrically conductive, i.e. containing 2.7% wt. of Vulcannanoparticles and 0.5% wt. of dimetoxycarboxy cellulose. The conductivecement sample shows a larger amount of narrow pores (<15 nm) and a loweramount of larger pores (range 15 to 35 nm) than the pure cement. Thisresult strongly suggests that the carbon nanoparticles fill the largerpores of the cement matrix, therefore increasing the number of narrowpores in the sample.

Mechanical Properties of Cement Samples:

The hardness (H), indentation modulus (M) and creep modulus (C) ofcement samples were determined using statistical micro-indentation(micro-combi, Anton Paar). Each sample is polished with a sequence ofSiC papers of decreasing abrasiveness, before being fixed on a metallicstub and stored at 60° C. for 24 h prior to testing. The micro-indenterconsists in a three-sided pyramid-like Berkovich diamond tip. The sampleis indented over a square grid of 15×15=225 indents, separated by 300 μmeach. Each indent is performed in a force-controlled mode, whichcorresponds to a typical indentation depth of 20 to 30 μm. The loadprofile is the following: the force is increased linearly at a fixedrate of about 14 mN/min until the desired load of 3N is reached. Theload is then maintained constant at the corresponding value for 180 s,before being ramped back down to zero at the same rate. The indentationmodulus and the hardness are computed from the raw curves following themethod of Oliver and Pharr. (3), (4). Finally, the creep modulus of thesamples was determined in analogy to the method proposed in reference(5), by fitting the creep phase indentation depth vs. time curve using alogarithmic function. The results for the reference cement samples arereported in FIG. 4A, and the results for the cement containing Vulcannanoparticles are reported in FIG. 4B. In brief the mechanicalproperties of the cement samples are neither affected by the addition ofcellulose, not by the addition of Vulcan carbon nanoparticles. Thedecrease in the mechanical properties above 1% wt. in particle content(FIG. 4B) is due to the increase in the water to cement ratio—see belowcaption of FIGS. 4A and 4B for details.

FIG. 4A: Hardness (H), Indentation modulus (M) and creep modulus (C) ofcement sample vs the content in dimetoxycarboxy cellulose. Samplesprepared with a water to cement ratio w/c=0.42. Tests performed onsamples after 45 days. The addition of cellulose up to 0.6% wt. does notimpact the mechanical properties of cement samples. FIG. 4B: same seriesof graphs for cement samples vs various content in Vulcan nanoparticles.Samples content in dimetoxycarboxy cellulose varies from 0.16 to 0.51.The water to cement ratio depends on the Vulcan content: w/c=0.43 forVulcan content<1% wt., w/c=0.52 for Vulcan content ranging between 1.6%wt. and 2.7% wt., and w/c=0.58 for Vulcan content of 3.1% wt. The changein mechanical properties around 1% wt. in Vulcan content is not relatedto the presence of carbon nanoparticles but results directly from theincrease of the water to cement ratio from 0.43 to 0.52. No changes inthe mechanical properties are observed beyond the percolation thresholdat about 2.3% wt. in Vulcan nanoparticles. Tests were performed onsamples of age ranging between 26 and 45 days. In both (a) and (b), eachpoint results from the average of at least 150 indentation tests anderror bars stands for the standard deviation. The content in bothcellulose and Vulcan nanoparticles is expressed as a percentage of thetotal weight content.

Further Experiment #1: Synthetic Procedures of Nanocomposite Cements

In a further experiment in accordance with an embodiment of theinvention, conductive cement samples are obtained through the dispersionof hydrophobic carbon black nanoparticles into a cement hydrophilicmedia. Carboxymetylcellulose helps to disperse large quantities of thehydrophobic carbon black nanoparticles in water. The overall procedureis depicted in FIG. 5 . The dispersant used is thecarboxymethylcellulose and was purchased from Aldrich and employedwithout purification (CAS number 9009-32-4). b) Three nanoporous carbonwere employed while being kindly provided by Cabot. c) The carboxymethylcellulose is first dissolved into deionized water under stirring, uponits complete dissolution (typically 6-8 hours) the carbon powders arethen introduced in whole. The native dispersion is let under stirringduring (3 days). A macroscopic homogenization is performed with aspatula after 24 and 48 hours in order to help the supernatant carbonpowder of being both entrapped into the native ink and well dispersed.It is not necessary of employing ultrasonic devices to foster thedispersion process. At the end of the dispersion process, homogeneousand shiny hydrophilic carbonaceous inks are obtained. d) to generatefinal carbonaceous-cement nanocomposites the native inks are introducedinto the Portland cement, the homogenization is reached while employinga ultraturax apparatus (Heidolph R21R 2102 Control) with a first 1minute 600 RPM regime and a final 1200 RPM regime is operated until thefinal pastes appear homogeneous by eyes (2 to 3 minutes for the volumesin use in this work). Finally, the native pastes are placed withinPlexiglas cylinder molds with paraffin films at the two extremities, andimmerged into Ca(OH)2 deionized water saturated solution for one week,prior being demolded.

Hereafter in this experiment the carboxymetylcellulose is labeled as CD,the Ketjen black carbon is labelled Ketj, the PBX 55 carbon is labeledPBX and the Vulcan XC72R is labeled W. Moreover, the synthesizedcarbon-cement nanocomposites are labeled hereafter[CDx(ketj-PBX-W)y(z)], where “x” refers to the CD weight percentageversus water, “y” refers to the carbon weight percentage versus waterand “(z)” represents the water/cement weight ratios. When the deionizedwater is replaced by a KOH alkaline solution, final composite materialsare labelled as followed: [CDx(ketj-PBX-W)y KOHwM(z)], where “w”emphasizes the solution molarity. When the carbon blacks are mixed, thematerials are labeled: [CDx(ketjA-PBXB-WC)y(z)] where A, B, C representthe weight ratio of carbon Ketj, PBX,W versus the total carbon blacks.

Specific Syntheses of Each Nanocomposite Are Proposed Below:

CD1W1 (0.43): 0.213 g of CD is dissolved into 21.53 g of deionizedwater. Upon dissolution completion 0.21 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD0.5W1 (0.43): 0.11 g of CD is dissolved into 21.53 g of deionizedwater. Upon dissolution completion 0.21 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD0.5W2 (0.44): 0.117 g of CD is dissolved into 21.97 g of deionizedwater. Upon dissolution completion 0.415 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD0.5W3 (0.42): 0.118 g of CD is dissolved into 21.09 g of deionizedwater. Upon dissolution completion 0.63 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1ketj1 (0.42): 0.209 g of CD is dissolved into 21.1 g of deionizedwater. Upon dissolution completion 0.217 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1Ketj2 (0.43): 0.214 g of CD is dissolved into 21.44 g of deionizedwater. Upon dissolution completion 0.429 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1.5Ketj3 (0.43): 0.328 g of CD is dissolved into 21.57 g of deionizedwater. Upon dissolution completion 0.64 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD2Ketj3 (0.43): 0.42 g of CD is dissolved into 21.34 g of deionizedwater. Upon dissolution completion 0.631 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD2Ketj3KOH1M (0.43): 0.42 g of CD is dissolved into 21.32 g of KOH 1Msolution. Upon dissolution completion 0.629 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD0.5W3KOH1M (0.43): 0.117 g of CD is dissolved into 21.33 g of KOH 1Msolution. Upon dissolution completion 0.631 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD2Ketj4 (0.43): 0.42 g of CD is dissolved into 21.47 g of deionizedwater. Upon dissolution completion 0.84 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD2Ketj3.4 (0.43): 0.42 g of CD is dissolved into 21.49 g of deionizedwater. Upon dissolution completion 0.73 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1Ketj0.5 (0.43): 0.21 g of CD is dissolved into 21.47 g of deionizedwater. Upon dissolution completion 0.107 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1.6W8 (0.52): 0.42 of CD is dissolved into 26 g of deionized water.Upon dissolution completion 1.68 g of W is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 50 gof cement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.6W5 (0.52): 0.42 g of CD is dissolved into 26 g of deionized water.Upon dissolution completion 1.26 g of W is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 50 gof cement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.6W6.4 (0.52): 0.42 g of CD is dissolved into 26 g of deionizedwater. Upon dissolution completion 1.68 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1.6Ketj8 (0.51): 0.42 g of CD is dissolved into 25.5 g of deionizedwater. Upon dissolution completion 2.1 g of Ketj is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1.5W9 (0.6): 0.42 g of CD is dissolved into 28.9 g of deionized water.Upon dissolution completion 2.52 g of W is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 50 gof cement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.6W2 (0.52): 0.42 g of CD is dissolved into 26 g of deionized water.Upon dissolution completion 0.415 g of W is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 50 gof cement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD0.8W5 (0.52): 0.208 g of CD is dissolved into 26 g of deionized water.Upon dissolution completion 1.26 g of W is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 50 gof cement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD0.8W6 (0.52): 0.208 g of CD is dissolved into 26 g of deionized water.Upon dissolution completion 1.68 g of W is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 50 gof cement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD2W4 (0.6): 0.6 g of CD is dissolved into 30 g of deionized water. Upondissolution completion 1.2 g of W is introduced and dispersed untilreaching a shiny homogeneous ink. This ink is then mixed with 50 g ofcement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.7W8 (0.6): 0.72 g of CD is dissolved into 43 g of deionized water.Upon dissolution completion 3.6 g of W is introduced and dispersed untilreaching a shiny homogeneous ink. This ink is then mixed with 71.5 g ofcement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.7W8 (0.8): 0.52 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 2.5 g of W is introduced and dispersed untilreaching a shiny homogeneous ink. This ink is then mixed with 37.5 g ofcement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.4PBX10 (0.6): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 3.0 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1.4PBX10 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 3.0 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

CD1.4PBX14 (0.6): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 4.15 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 50 g of cement powder to form a homogenized paste, that is cast andstored as described in FIG. 5 .

CD1.7PBX14 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 4.18 g of W is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

CD1.4 (ketj0.2W0.8)12 (0.6): 0.42 g of CD is dissolved into 30 g ofdeionized water. Upon dissolution completion 2.88 g of W and 0.72 g ofketj are introduced and dispersed until reaching a shiny homogeneousink. This ink is then mixed with 50 g of cement powder to form ahomogenized paste, that is cast and stored as described in FIG. 5 .

CD1.4 (ketj0.2W0.8)12 (0.8): 0.42 g of CD is dissolved into 30 g ofdeionized water. Upon dissolution completion 2.88 g of W and 0.72 g ofketj are introduced and dispersed until reaching a shiny homogeneousink. This ink is then mixed with 37.5 g of cement powder to form ahomogenized paste, that is cast and stored as described in FIG. 5 .

CD1.4W8 (0.7): 0.42 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 2.5 g of W is introduced and dispersed untilreaching a shiny homogeneous ink. This ink is then mixed with 42.86 g ofcement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.4W8 (0.65): 0.42 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 2.5 g of W is introduced and dispersed untilreaching a shiny homogeneous ink. This ink is then mixed with 46.15 g ofcement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.4W8 (0.90): 0.42 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 2.5 g of W is introduced and dispersed untilreaching a shiny homogeneous ink. This ink is then mixed with 33.33 g ofcement powder to form a homogenized paste, that is cast and stored asdescribed in FIG. 5 .

CD1.4PBX18 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 5.30 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

CD1.4PBX21.5 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 6.15 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

CD1.4PBX2 (0.8): 0.42 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 0.6 g of PBX is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 37.5g of cement powder to form a homogenized paste, that is cast and storedas described in FIG. 5 .

CD1.4PBX6 (0.8): 0.42 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 1.8 g of PBX is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 37.5g of cement powder to form a homogenized paste, that is cast and storedas described in FIG. 5 .

CD1.4PBX8 (0.8): 0.42 g of CD is dissolved into 30 g of deionized water.Upon dissolution completion 2.4 g of PBX is introduced and disperseduntil reaching a shiny homogeneous ink. This ink is then mixed with 37.5g of cement powder to form a homogenized paste, that is cast and storedas described in FIG. 5 .

CD1.4PBX12 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 3.6 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

CD1.4PBX16 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 4.8 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

CD1.4PBX20 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 6.0 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is then mixedwith 37.5 g of cement powder to form a homogenized paste, that is castand stored as described in FIG. 5 .

Further Experiment #2: Electronic Transport Properties ofCement/Nanoporous Carbon Nanocomposites

In a further experiment in accordance with an embodiment of theinvention, there is first discussed the electrical conductivityproperties of the cement/carbon-back composites (w/c=0.8) prepared withvarious concentrations in carbon black (PBX 55, Cabot) ranging between 0and 8.12% wt. for a fixed cellulose content of 0.6% wt. Resistivitymeasurements were performed on cylindrical samples (thickness of about0.8 cm and diameter of about 2 cm), which surfaces have been polisheddown to the micron scale. The samples are sandwiched between conductivegraphite layers, each connected to a power source. A ramp of voltagefrom 5V to 0V is performed on each sample, which allows us to determinethe composite conductivity using Ohm's Law and the exact geometricdimensions of each sample. For each sample, we measure the open circuitvoltage before and after the voltage ramp to estimate the polarizationof the sample induced by the ramp. Finally, for each sample, theelectrical conductivity is measured first at ambient temperature andstandard humidity level, and second after the sample has been dried at60° C. during 2 weeks. The results are presented in FIG. 6 .

FIG. 6 shows resistivity of hardened cement paste/nanoporous carboncomposites containing 0.6% wt. of carboxymethyl-cellulose and variousamounts of nanoporous carbon nanoparticles ranging between 0 and 8% wt.(a) Resistivity of standard and dried composites. Standard compositesdisplay both ionic and electronic conduction, whereas the driedcomposites only display electronic conduction. The red dashed linehighlights the critical carbon content above which dried composites areelectronically conductive due to the presence of a percolated network ofnanoporous carbon nanoparticles within the matrix of hardened cementpaste. (b) Open circuit voltage Ū_(opc) measured before and after thevoltage ramp for standard composites vs nanoporous carbon content.Ū_(opc) is larger after the voltage ramp, showing that the composite hasbeen polarized by the voltage ramp. (c) Ū_(opc) measured before andafter the voltage ramp for dried composites vs nanoporous carboncontent. Above the percolation threshold, Ū_(opc) is identical beforeand after the voltage ram and equal to zero. Experiments performed on 30day old samples.

Measuring the open circuit voltage of the cement/nanoporous carboncomposites confirms the above finding. Indeed, open circuit voltagemeasurements performed on dried composites show that samples withcontent in nanoporous carbon nanoparticles larger than 3% wt. exhibit anopen circuit voltage equal to zero both before and after the voltageramp (FIG. 6C). This result strongly supports the idea that thecomposite contains a percolated network of nanoporous carbon particlesspanning through the entire sample that allows any electronicpolarization (pre-existing or induced by the voltage ramp) to relaxquickly via electronic conduction. Note that the same compositesconsidered in standard conditions (i.e. without being dried) display anegligible polarization before the voltage ramp, while they develop anopen circuit voltage of about 0.5V after the ramp due to the presence offree water and ions (FIG. 6B). Such polarization effect vanishes forcomposites containing more than 8% wt. of nanoporous carbonnanoparticles, where the electrical conductivity due to the percolatednetwork of nanoporous carbon nano-particles dominates the ionicconductivity. This result strongly suggests that the most promisingcomposites for building electrodes are samples containing carbon inlarger amount than 8% wt.

Finally, note that the existence of a critical concentration innanoporous carbon nano-particles beyond which the composite iselectrically conductive is reported here on samples prepared exclusivelywith one type of nanoporous carbon nanoparticles (i.e. PBX 55).Nonetheless, our results extend to other types of nanoporous carbonnanoparticles, as illustrated in FIG. 7 on Vulcan XC72R as well asVulcan XC72R and Ketjenblack mixtures. The composite samples prepared(for w/c=0.52) with Vulcan XC72R nanoporous carbon particles show aninsulator/conductor transition at about 2.5% wt. This value is lowerthan that reported for PBX 55 in FIG. 6 , but one should keep in mindthat the samples reported in FIGS. 6 and 7 were not prepared with thesame water to cement ratio (w/c=0.8 and w/c=0.52 respectively).Therefore, the critical concentration in carbon particles to turn thecomposite into a conductive material depends on the water to cementratio as illustrated in FIG. 7 in the case of the Vulcan XC72R (see bluesymbols and dashed curves). A composite sample prepared with the VulcanXC72R and a water to cement ratio of 0.58 is conductive, whereas asimilar sample prepared with w/c=0.8 (with roughly every other parameterkept the same) is non-conductive.

This result strongly suggests that the insulator/conductor transition ismoved to higher carbon content for larger water to cement ratio.Finally, note that composite samples prepared with sufficiently largeamount of Vulcan XC72R, or mixtures of Vulcan XC72R and KetjenBlack orPBX also display a low resistivity, similarly to what was shown forcomposites prepared with PBX 55 as reported above in FIG. 6 .

FIG. 7 shows the resistivity of a broad collection of compositesprepared with various water to cement ratio (w/c), various amount ofcarboxymethyl-cellulose and various type and amounts of carbonnano-particles. All the measurements reported here were performed onnon-polished samples dried at 60° C. for at least 1 week. Compositesamples prepared with Vulcan XC72R show an insulator/conductortransition at about 2.5% wt. Experiments performed on samples of 30 daysold at least.

Further Experiment #3: Mechanical Properties of Cement/Carbon Composites

In a further experiment in accordance with an embodiment of theinvention, there is discussed the impact of both carboxymethyl-celluloseand nanoporous carbon nanoparticles on the mechanical properties ofhardened cement paste at two different spatial scales: at the microscale(˜20 μm) and at the nanoscale (˜300 nm). In both cases, the linear andthe non-linear mechanical properties, i.e. the indentation modulus M andthe hardness H, and the creep modulus C are determined by statisticalindentation. The data are analyzed following the methods developed byOliver & Phaar to compute H and M, and that of Vandamme & Ulm forcomputing C. All the experiments were performed on a hardened cementpaste with a water to cement ratio w/c=0.8 and a cellulose content of0.6% wt. The nanoporous carbon used is PBX 55, which amount was variedbetween 0 and 8.12% wt.

FIG. 8 shows mechanical properties of hardened cement paste, i.e.distribution of Hardness H, indentation modulus M and creep modulus Cdetermined at the mesoscale (a) to (c) and at the microscale (d) to (f).Data reported in (a), (b) and (c) were obtained by performing 15×15=225indents of typical depth 15 μm, and separated by 300 μm. Data reportedin (d), (e) and (f) were obtained by performing 21×21=441 indents oftypical depth 300 nm, and separated by 10 μm. Experiments performed on asample of 30 days old.

Hardened cement paste alone displays homogeneous properties at themesoscale, whereas it exhibits heterogeneous properties at themicroscale. Indeed, H, M and C show a Gaussian distribution at themesoscale (FIGS. 8A, 8B, and 8C) whereas H, M and C exhibit a morecomplex distribution at the microscale that can be fitted by 4independent Gaussian distributions (FIGS. 8D, 8E and 8F). It has beenshown in the literature that these 4 distributions correspond to the 4phases from which hardened cement paste is made of

These phases are respectively low-density CSH (Calcium Silica Hydrate),high density CSH, Calcium Hydroxyde and the clinker originallyintroduced and that display the strongest mechanical properties. These 4phases form domains of spatial extension that is typically of a fewmicrons, which is why these domains are not “visible” when performingindentation at the mesoscale. These results are used as a reference todetermine the impact of cellulose and nanoporous carbon nanoparticles.

The addition of 0.6% wt. of carboxymethyl cellulose leads to asignificant broadening of the distribution of H, M and C at themesoscale. Moreover these distributions are no longer Gaussian (FIG. 9). FIG. 9 shows distribution of H, M and C at the mesoscale for thereference hardened cement paste (same data as in FIGS. 8A, 8B and 8C)and for the cement paste/cellulose composite. Data reported in (a), (b)and (c) were obtained by performing 15×15=225 indents of typical depth15 μm, and separated by 300 μm. The presence of cellulose results innon-Gaussian distribution of broader extent. Experiments performed on asample of 30 days old.

This result shows that cellulose has a significant impact on thehydration process of cement paste and strongly suggests that the phasescomposing the cement paste must have a greater spatial extent inpresence of cellulose. Indeed, indentation at the microscale revealsthat there are only 3 phases left: low density and high density CSHtogether with Calcium Hydroxyde (FIG. 6 ). The clinker has beencompletely consumed, which proves that the presence of cellulosestrongly favors the hydration of cement. Moreover, the spatial extent ofthe two following phases: low density and high density CSH is indeedmuch larger in presence of cellulose, as illustrated in FIG. 6 , wherewe can see that domains for both phases can be as large as 200 μm, whichis consistent with the broadening of the distribution of H, M and C atthe mesoscale.

Finally, we shall emphasize that the presence of 0.6% wt. cellulose inthe hardened cement paste poorly affects the most probable value of Hand M both at the mesoscale (FIG. 9 ) and at the microscale (FIG. 10 ).However, the most probable value for the creep modulus decreases towardslower values at the mesoscale.

FIG. 10 shows distribution of H, M and C at the microscale for acement/cellulose composite (a)-(c). Data reported in (a), (b) and (c)were obtained by performing 21×21=441 indents of typical depth 300 nm,and separated by 10 μm. The Gaussian fits of the data correspond to thethree different phases composing the material: low density CSH (cyan),high density CSH (red) and calcium hydroxide (yellow). The total numberof phases was determined by a Gaussian Mixture Modelling approachcoupled to a Bayesian statistical criteria. An optical map of theindentation grid is pictured in (d), while the location of the threedifferent phases are pictured in (e). Note that both low and highdensity CSH (cyan and red respectively) show domains of size comparableto the whole map, i.e. about 200 μm. Experiments performed on a sampleof 30 days.

We now discuss the impact of nanoporous carbon nanoparticles on themechanical properties of the composites. For samples of 30 days old, thepresence of nanoporous carbon nanoparticles reinforces the mechanicalproperties of hardened cement paste (w/c=0.8) at the mesoscale. Indeed,H, M and C increases linearly with the amount of nanoporous carbonnanoparticles. Similarly, the fracture toughness of the composite, whichis measured by scratch tests, also increases linearly with the amount ofnanoporous carbon nanoparticles (FIG. 11 ).

FIG. 11 shows evolution at the mesoscale of the mechanical properties ofcement/carbon composites vs the amount of carbon. (a) Hardness H, (b)Indentation modulus M, (c) Creep modulus C, (d) Fracture toughness K_(c)vs nanoporous carbon nanoparticles content. Symbols encode the sampleage: bullets=30 days, and stars=60 days. Colors encode the compositionof the sample: white=hardened cement paste, gray=hardened cement pasteand cellulose, black=hardened cement paste+cellulose+nanoporous carbon.The error bars stand for the width of the distributions of each quantityof interest. The red dashed line corresponds to the best linear fit ofthe data.

At 60 days, the mechanical properties of the composites are identical tothat of 30 days. In contrast, the sole hardened cement paste showsimproved mechanical properties at 60 days compared to 30 days, exceptfor the fracture toughness, which keeps the same value. The keydifference between the composite and the hardened cement paste resultsfrom the presence of the cellulose, which foster the hydration of thecement. The composite samples exhaust the reactive cement paste fasterthan the pure cement paste, whose properties keep evolving beyond 30days. This effect is only linked to the presence of cellulose and, as akey result, the presence of carbon nanoparticles within the matrix ofhardened cement paste does not degrade the mechanical properties ofhardened cement paste. Our results prove that the addition of carbonnanoparticles does not weaken the mechanical properties of hardenedcement paste, including beyond the critical value of 3% for which thecarbon particles form a percolated network within the matrix of hardenedcement paste.

As a last series of tests, we have determined the mechanical propertiesof the composites at the microscale. In agreement with the resultsreported in FIG. 10 and obtained on the hardened cement paste inpresence of cellulose, we observe that there is no clinker left in thecomposites and that the sample composition is dominated by low densityCSH, high density CSH and calcium hydroxide (FIG. 12 ). However, theGaussian Mixture Modelling of the data coupled to a Bayesian informationcriteria reveals the presence of a fourth phase, which we interpret asthe carbon nanoparticles, given the values of H, M and C for this fourthphase. Interestingly, the indentation grid reveals that the carbonnano-particles are well-dispersed within the sample (FIG. 12E). Inconclusion to the section on mechanical properties, we have shown thatthe presence of cellulose fosters the hydration of the cement paste andleads to the complete consumption of the clinker initially present. Thecellulose mainly speeds up the hydration process, while poorly impactingat the mesoscale the hardness and the indentation modulus of theresulting material. The presence of nanoporous carbon nano-particlesreinforces the overall mechanical properties of the hardened cementpaste, which increases linearly with increasing carbon content. Theexistence of a sample-spanning percolated network beyond 3% wt. ofnanoporous carbon nanoparticles does not impact the mechanicalproperties of the composite, which proves that these electricallyconductive composites can be used in the design of a structuralsupercapacitor.

FIG. 12 shows distribution of H, M and C at the microscale for acomposite with 0.6% wt. cellulose and 5% wt carbon (a)-(c). Datareported in (a), (b) and (c) were obtained by performing 21×21=441indents of typical depth 300 nm, and separated by 10 μm. The Gaussianfits of the data correspond to the four different phases composing thematerial: low density CSH (cyan), high density CSH (red), calciumhydroxide (yellow) and carbon (green). The total number of phases wasdetermined by a Gaussian Mixture Modelling approach coupled to aBayesian statistical criteria. An optical map of the indentation grid ispictured in (d), while the location of the four different phases arepictured in (e). Note that the nanoporous carbon nanoparticles are welldispersed and localized in the vicinity of the calcium hydroxide.Experiments performed on a sample of 30 days old.

Further Experiment #4: Heat Transport Properties of Cement/NanoporousCarbon Composites

In a further experiment in accordance with an embodiment of theinvention, by polarizing a 1 cm³ sample of one of ourelectron-conducting cement/nanoporous carbon composites with 30 V(direct current, 1 A), we obtained an immediate increase of sample'sexternal surface temperature by 5 Celcius as shown in FIG. 13 . FIG. 13shows surface temperature increase of a cellulose +5% wt carbon sampleunder 30 V (DC). This shows that a possible application of an embodimentof the invention as a solution to prevent freeze-thaw of pavements if athin (centimeter thick) layer of our cement/carbon nanocomposite were tobe deposited on pavement slab and connected to an external source ofelectric current (that could be from solar panels for instance). Anotherapplication will be in the field of construction where an embodiment ofthe invention can be used to protect basement walls for instance fromcapillary (water) rise.

Further Experiment #5: Supercapacitor in Cement/Nanoporous CarbonComposites

Cement/nanoporous carbon nano-composites also have the ability totransform a cement paste into an electrical energy storage device suchas a structural supercapacitor turning cement from mere buildingmaterial into an electrical energy storage structural element device. Anembodiment according to the invention comprises a structuralsupercapacitor based on the cement and nanoporous carbon compositestaught herein, that will be optimized for their capacitance andstructural performance under the form of a self-standing rigidelectrodes system. A structural supercapacitor generally requires atleast two multifunctional components: a structural electrode with highand ionically accessible surface area and good electronic conductivity.This is the case of the nanoporous carbon/cement composites of anembodiment, which in addition demonstrate with no loss of mechanicalproperties. FIG. 14 shows the capacitor effect (as obtained from cyclicvoltammetry experiment, CV) with KCl 1M as electrolyte. Our cementnanoporous carbon composite allows charge-discharge cycling. In FIG. 14, there are shown cyclic voltammetry measurements on the sampleCD1.4PBX20 (0.8): 0.42 g of CD is dissolved into 30 g of deionizedwater. Upon dissolution completion 6.0 g of PBX is introduced anddispersed until reaching a shiny homogeneous ink. This ink is thenintroduced into 37.5 g of cement and homogenized, molded and stored asdescribed in FIG. 5 .

An embodiment can be optimized in all aspects ranging from the choiceand concentration of the electrolyte (for example, water, acetonitrilesolvent and ionic species, such as alkali, ionic liquids) to the amountand type of nanoporous carbons, dispersant (for example cellulose basedpolymers) to the initial water/cement binder ratio. The percolatingphase of nanoporous carbon nanograins dispersed in a cement paste canpotentially have a large absolute capacitance given the size ofstructural elements used in the built infrastructure. It can be alsoused as battery.

REFERENCES

(1) Brunauer, S., Emmett, P. H., & Teller, E. (1938). Adsorption ofgases in multimolecular layers. Journal of the American ChemicalSociety, 60 (2), 309-319.

(2) Barrett, E. P., Joyner, L. G., & Halenda, P. P. (1951). Thedetermination of pore volume and area distributions in poroussubstances. I. Computations from nitrogen isotherms. Journal of theAmerican Chemical Society, 73(1), 373-380.

(3) Oliver, W. C., & Pharr, G. M. (1992). An improved technique fordetermining hardness and elastic modulus using load and displacementsensing indentation experiments. Journal of Materials Research, 7,Cambridge Univ. Press 6, 1564-1583.

(4) Oliver, W. C., Pharr, G. M., & Teller, E. (2004). Measurement ofhardness and elastic modulus by instrumented indentation: Advances inunderstanding and refinements to methodology. Journal of MaterialsResearch, Cambridge Univ. Press 19, 3-20.

(5) Vandamme, M., Ulm, F.-J., & Teller, E. (2009). Nanogranular originof concrete creep. Proceedings of the National Academy of Sciences, 26,10552-10557.

The teachings of all patents, published applications and referencescited herein are incorporated by reference in their entirety.

While example embodiments have been particularly shown and described, itwill be understood by those skilled in the art that various changes inform and details may be made therein without departing from the scope ofthe embodiments encompassed by the appended claims.

What is claimed is:
 1. A method of forming an electrically conductivecement composite, the method comprising: mixing nanoporous carbonnanoparticles in an aqueous solution of a carbon nanoparticle dispersingagent thereby creating a nanoporous carbon nanoparticle suspension; andmixing a hydraulic cement powder with the nanoporous carbon nanoparticlesuspension.
 2. The method of claim 1, further comprising casting theelectrically conductive cement composite and immersing the electricallyconductive cement composite in a solution comprising lime and water. 3.The method of claim 1, comprising forming a composite comprising betweenabout 2% by weight and about 10% by weight of the nanoporous carbonnanoparticles with respect to a total initial mix comprising thehydraulic cement, the carbon nanoparticle dispersing agent, the waterand the nanoporous carbon nanoparticles, and comprising a water tocement ratio between about 0.5 and about 0.8.
 4. The method of claim 1,wherein the carbon nanoparticle dispersing agent comprises carboxymethylcellulose.
 5. The method of claim 4, wherein the carboxymethyl cellulosecomprises between about 0.1% by weight and about 1% by weight of a totalinitial mix comprising the hydraulic cement, the carbon nanoparticledispersing agent, the water and the nanoporous carbon nanoparticles. 6.The method of claim 1, wherein the nanoporous carbon nanoparticlescomprise a pore size of less than about 1 nanometer.
 7. The method ofclaim 1, wherein the nanoporous carbon nanoparticles comprise at leastone of: Vulcan carbon black, Ketjen carbon black, PBX carbon black andan activated porous carbon.
 8. The method of claim 1, wherein the cementcomprises Portland Cement.
 9. The method of claim 8, wherein theelectrically conductive cement composite comprises between about 50% byweight and about 70% by weight of Portland Cement with respect to atotal initial mix comprising the hydraulic cement, the carbonnanoparticle dispersing agent, the water and the nanoporous carbonnanoparticles.
 10. The method of claim 1, wherein the nanoporous carbonnanoparticles comprise a specific surface area less than about 3000m²/g.